This application is based on patent applications Hei.10-161083 and Hei.11-118343 filed in Japan, the contents of which are hereby incorporated by references.
1. Field of the Invention
The present invention relates to an optical sensor including a sensor module and a flexible printed circuit substrate and relates to an optical unit including the optical sensor and a base member.
2. Description of the Related Art
An optical unit for sensing an incident light and for outputting an electric signal corresponding to the sensed light is generally known. In such the optical unit, a sensor chip such as a CCD or photodiodes having an array of photo-sensing devices is contained in a package. Output terminals are formed for penetrating walls of the package. Inside ends of the output terminals are connected to the sensor chip in the package, and outside ends of the output terminals are connected to conductive patterns on a flexible printed circuit substrate outside of the package. Thus, output signals from the photo-sensing devices can be transmitted to an external circuit via the output terminals and the flexible printed circuit substrate.
As known, for example, from an automatic focusing (hereinafter abbreviated as AF) sensor, the optical sensor is generally used with other optical elements such as a lens, a mirror, and so on for guiding the incident light to the sensor chip. In a conventional optical unit, the sensor chip is contained in the package, so that it is necessary to place a photo-sensing surface of the sensor chip perpendicular to an optical axis of the optical elements by adjusting a position of the package with respect to the optical elements. However, the adjustment of the position of the package is difficult because it is connected to the flexible printed circuit substrate.
Furthermore, in recent years, it is desired to make a size of a camera be much smaller and thinner in the market. Accordingly, it is further desired to downsize the optical unit which is to be provided in the camera. However, the downsizing of the optical unit has a limit, since the sensor chip is enclosed by the package and the package has a volume. Then, it is proposed to omit the package and to connect the photo-sensing devices of the sensor chip directly on the circuit on the flexible printed circuit substrate further for downsizing the optical unit.
When the package is omitted, the sensor chip is directly held on the flexible printed circuit substrate. The flexible printed circuit substrate, however, has insufficient strength to hold the sensor chip directly, so that it is difficult to assemble the flexible printed circuit substrate with the sensor chip at a predetermined position with respect to the optical elements in the optical unit and to adjust the photo-sensing surface of the sensor chip to be perpendicular to the optical axis if the optical elements. Furthermore, the sensor chip on the flexible printed circuit substrate is directly exposed, so that it is necessary to shield undesirable incident light reaching to the photo-sensing surface of the sensor chip except from an exit opening of the base member of the sensor unit.
An object of the present invention is to provide an optical sensor in which a flexible printed circuit substrate holding a sensor chip is reinforced for having a sufficient strength so as to be treated in an assemble process without using any package.
Another object of the present invention is to provide an optical unit in which the photo-sensing surface of the sensor chip of the above-mentioned optical sensor is positioned at predetermined distance with respect to optical elements held on a base member and the optical sensor is shielded from the external light except the exit opening of the base member.
Still another object of the present invention is to provide a sensor unit which has a sufficient strength.
An optical sensor in accordance with the present invention comprises: a sensor module including a sensor chip having at least a photo-sensing device provided thereon and a flexible printed circuit substrate having conductive patterns to which the photo-sensing device is connected; and a sensor holder for positioning the sensor module at a light exit opening portion of a base member of an optical unit which holds at least an optical element for guiding an incident light to the sensor module.
Furthermore, an optical unit in accordance with the present invention comprises: a sensor module including a transparent plate, a sensor module having at least a photo-sensing device and a flexible printed circuit substrate having conductive patterns to which the photo-sensing device is connected, and wherein the sensor chip is disposed for facing the transparent plate through an opening of the flexible printed circuit substrate; a base member for holding at least an optical element which guides an incident light to the sensor module, and having a positioning portion to which another surface of the transparent plate contacts for positioning the sensor chip with respect to the optical element and a fixing portion to which the sensor holder is fixed; and a sensor holder for positioning the sensor module at a light exit opening portion of the base member.
Moreover, a sensor unit in accordance with the present invention comprises: a transparent plate capable of transmitting light; a sensor chip provided with a photo-sensing device for sensing light transmitted through the transparent plate, the sensor chip being fixedly attached with the transparent plate; a flexible printed circuit substrate electrically connected with the photo-sensing device; and a holder fixedly attached on the transparent plate, the holder having a shape capable enclosing the sensor chip.
Another sensor unit in accordance with the present invention comprises: a transparent plate capable of transmitting light; a holder fixedly attached with the transparent plate on one side thereof, the holder being formed with an opening; a sensor chip provided with a photo-sensing device for sensing light passed through the opening and the transparent plate, the sensor chip being fixedly attached to the other side of the holder; and a flexible printed circuit substrate electrically connected with and fixedly attached to the sensor chip.
Since the sensor holder serves as reinforcing member of the sensor module or the flexible printed circuit substrate with the sensor chip, the sensor module has sufficient strength so that it is treated in the assemble process. Furthermore, the sensor chip can directly be positioned at the light exit opening portion of the base member of the optical unit by the sensor holder, so that it becomes easy to assemble the flexible printed circuit substrate with the sensor chip at a predetermined position with respect to the optical elements in the optical unit and to adjust the photo-sensing surface of the sensor chip to be perpendicular to the optical axis if the optical elements. As a result, a package conventionally used can be omitted, so that the optical sensor or the optical unit can be made much smaller and thinner. Furthermore, when the optical sensor or the optical unit is used in an equipment, the equipment can consequently be made much smaller and thinner than the conventional one.